The proposed Clinical Core is designed with the objectives of: recruiting healthy controls and subjects; providing a central service for pulmonary function assessment, methacholine challenges, antigen skin testing, and bronchoprovocation; providing a central service for standardized collection of bronchoalveolar lavage fluid, for cellular analysis, and for distribution of samples to the investigators in Projects 1, 2, and 6; coordinating the retrieval and distribution of tissue specimens from patients receiving bronchial lung biopsies; and finally, providing quality control for the collection, computer entry, and storage of data.